Ace brand muriatic acid from my local ace.
Transchem Muriatic Acid 1 gal Liquid - Ace Hardware
Professional Strength 31.45% HCL (Muriatic Acid), excellent for pH reduction in swimming pools or to clean and etch masonry surfaces, excellent for pH reduction in all commercial and residential pools.Find the ACID MURIATIC GAL at Ace.
www.acehardware.com